The cotton-top tamarin, which develops a spontaneously occurring colitis, is a valuable animal model for the study of human inflammatory bowel disease. Elucidation of the mechanisms involved in the development of colitis and identification of the contribution of dietary factors and microbiologic agents are important components in the study of the pathogenesis of this disease. Anecdotal information suggests that cotton-top tamarins fed Zu/Preem marmoset diet have a higher incidence of colitis than animals fed Spectrum marmoset diet. The diets differ primarily in cholesterol and water content. The bacterium, Campylobacter jejuni has also been implicated as an etiologic agent in colitis. The objective of this study is to determine if cotton-top tamarins fed the commercially available Zu/Preem marmoset diet have a significantly greater incidence of spontaneously occurring colitis as compared to tamarins which are fed the commercially available Spectrum Marmoset diet, and to ascertain if there is an association between positive Campylobacter jejuni culture and colitis. Baseline physical examination, body weight measurement, colon biopsy, and rectal culture for Campylobacter jejuni were obtained from each animal. Colon biopsies were processed for histologic examination and were graded on a scale of 0 to 3 (0=normal; 1=mild, 2=moderate, 3=severe colitis). All animals with grade 2 or higher colitis were excluded from study. All rectal cultures were negative for Campylobacter jejuni. Ninety-two animals (83 with no colitis and 9 with grade 1 colitis) were randomized into 2 groups by age and sex. One group is fed Zu/Preem marmoset diet and the other group is fed Spectrum marmoset diet. Animals will be monitored at 3 month intervals by physical examination, body weight measurement, colon biopsy, and rectal culture to determine if there is a difference between the two groups in the incidence of colitis or other parameters over time.